U.S. patent number 4,440,173 [Application Number 06/280,222] was granted by the patent office on 1984-04-03 for programmable body stimulation system.
This patent grant is currently assigned to Medtronic. Invention is credited to Jerome T. Hartlaub, Lawrence C. Hudziak.
United States Patent |
4,440,173 |
Hudziak , et al. |
April 3, 1984 |
**Please see images for:
( Certificate of Correction ) ** |
Programmable body stimulation system
Abstract
A body stimulation system including external components for
generating and transmitting programming signals and implantable
components including a signal generator with at least one alterable
operating characteristic, a stimulation signal delivering system
and circuit responsive to receive programming signals for
establishing the operating characteristic in predetermined
correspondence therewith. The stimulation signal delivering system
is connected to the operating characteristic establishing circuitry
for receiving the programming signals. In a preferred embodiment,
the external components are prevented from transmitting programming
signals during a stimulation signal and, more preferably, for a
predetermined period following a stimulation signal. The
predetermined period may be established such that the external
system is activated during the refractory period of the tissue
being stimulated. The external system may provide a programming
signal and a second signal having characteristics discriminable
from the characteristics of the programming signal such that the
operating characteristic establishing circuitry is responsive to a
received programming signal only during the occurrence of the
second signal. The pulse generator of the implantable unit may also
respond to the second signal to operate at a fixed rate during the
second signal.
Inventors: |
Hudziak; Lawrence C. (White
Bear Lake, MN), Hartlaub; Jerome T. (New Brighton, MN) |
Assignee: |
Medtronic (Minneapolis,
MN)
|
Family
ID: |
26785580 |
Appl.
No.: |
06/280,222 |
Filed: |
July 6, 1981 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
92354 |
Nov 8, 1979 |
|
|
|
|
Current U.S.
Class: |
607/30 |
Current CPC
Class: |
A61N
1/37252 (20130101) |
Current International
Class: |
A61N
1/372 (20060101); A61N 001/36 () |
Field of
Search: |
;128/419PG |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kamm; William E.
Attorney, Agent or Firm: Schroeder, Siegfried, Vidas &
Arrett
Parent Case Text
This is a continuation of parent application Ser. No. 92,354, filed
on Nov. 8, 1979 in the name of Lawrence Hudziak et al., now
abandoned.
Claims
We claim:
1. In a body stimulation system of the type having external means
for generating and transmitting radio frequency programming signals
and implantable means, the implantable means including signal
generator means with at least one programmable operating
characteristic and means responsive to received programming signals
for establishing said programmable operating characteristic in
predetermined correspondence therewith; a housing enclosing said
signal generator; and output means for delivering stimulation
signals to a desired body site including stimulation delivering
lead means extending from said housing, the improvement wherein
said lead means comprises means connected to said operating
characteristic establishing means for receiving said programming
signals.
2. The body stimulation system of claim 1 wherein said external
means comprises means for preventing the transmission of
programming signals during a stimulation signal.
3. The body stimulation system of claim 2 wherein said transmission
preventing means comprises means for preventing transmission of
programming signals for a predetermined period following a
stimulation signal.
4. The body stimulation system of claim 1 comprising means for
activating said external means during the refractory period of the
tissue at said desired body site.
5. The body stimulation system of claim 1 comprising means for
rendering said output parameter establishing means responsive to
received programming signals only during the occurrence of second
externally generated signals having characteristics discriminable
from the characteristics of said programming signals.
6. The body stimulation system of claim 5 wherein said programming
signals comprise radio frequency signals and said second signal
comprises magnetic signals.
7. The body stimulation system of claim 5 wherein said signal
generator means comprises pulse generator means, said pulse
generator means operating at a fixed rate during said second
externally generated signals.
8. The body stimulation system of claim 7 wherein said external
means comprises means for preventing the transmission of
programming signals during a stimulation signal.
9. The body stimulation system of claim 8 wherein said transmission
preventing means comprising means for preventing transmission of
programming signals for a predetermined period following a
stimulation signal.
10. The body stimulation system of claim 9 wherein said programming
signals comprise radio frequency signals and said second signal
comprises magnetic signals.
11. The body stimulation system of claim 7 comprising means for
activating said external means during the refractory period of the
tissue at said desired body site.
Description
BACKGROUND OF PRIOR ART
Programmable body implanatable stimulators are known to the prior
art. Their programming has been variously accomplished as through
the use of a magnetic field operating on an implanted reed switch,
the use of radio frequency energy transmitted to an antenna within
the implanted unit and through the use of a Keith needle. A
magnetic field alone has the obvious disadvantage of being easily
duplicated by extraneous fields to result in an undesired
programming. A Keith needle requires a penetration of the body. The
radio frequency energy approach, as implemented in the prior art,
has also had its drawbacks.
One system which combines a magnetic field with a radio frequency
signal for the programming of a body implantable stimulator is
disclosed in U. S. Pat. No. 4,066,086 issued Jan. 3, 1978, to
Clifton A. Alferness et al. for PROGRAMMABLE BODY STIMULATOR, which
is hereby incorporated by reference. Another programmable unit is
disclosed in application Ser. No. 957,813 now U.S. Pat. No.
4,275,737 filed Nov. 6, 1978, in the name of Jerome T. Hartlaub et
al. for DEMAND CARDIAC PACEMAKER HAVING REDUCED POLARITY DISPARITY,
which is commonly owned with the present invention and which is
also incorporated herein by reference.
Many prior art implantable stimulators have been formed by molding
the components, including mechanical and electrical connections for
the lead, in a matrix of encapsulating material which supports the
components and shields them from the body environment. Typically,
the encapsulating material is an epoxy. However, it is generally
recognized that an enclosed and hermetically sealed unit is more
reliable as a result of the known and controlled environment
provided by the hermetic seal. For this reason, many recent signal
generator designs include a rigid enclosure formed of a plurality
of preformed members which are typically welded together to
complete the enclosure. In the context of a programmable unit,
however, absorption, reflection and attenuation of radio frequency
energy by the metal enclosure complicates the programming
operation. These programming problems are further compounded by
power transmission limits established by the FCC and the trend
towards smaller and smaller units.
BRIEF SUMMARY OF THE INVENTION
The present invention is directed to a body stimulation system of
the type having an external unit for generating and transmitting
radio frequency programming signals and an implantable unit
including a stimulation signal generator with at least one
alterable operating characteristic, an output system for delivering
a stimulation signal to the desired body site and circuitry
responsive to received programming signals for establishing the
operating characteristic in predetermined correspondence therewith.
The output delivering system is connected to the operating
characteristic establishing circuitry and receives the programming
signals and delivers the same to the operating characteristic
establishing circuitry. In a preferred embodiment, the output
delivering system includes a stimulation delivering lead, the lead
receiving and delivering the programming signals to the operating
characteristic establishing circuitry. Thus, antenna coils of prior
art programmable devices are eliminated, without elimination of
their function. In addition, in the event that the stimulation
signal generator is hermetically sealed in a housing, as described
above, that housing does not interfere with the reception of the
programming signals by the implantable device. To assure the
integrity of the programming signal, the external device is
prevented from transmitting a programming signal during a
stimulation signal. Preferably, such transmission is prevented for
a predetermined time following a stimulation signal. The
predetermined period may be such that the external device is
activated to transmit a programming signal only during the
refractory period of the tissue being stimulated. In order to limit
programming of the implantable device by extraneous signals, the
operating characteristic establishing circuitry may be rendered
responsive to receive programming signals only during the
occurrence of second externally generated signals having
characteristics discriminable from the characteristics of the
programming signals. In a preferred embodiment, the programming
signals comprise radio frequency signals and the second signals
comprise magnetic signals. In the event that the stimulation signal
generator is a pulse generator, it may be caused to operate at a
fixed rate during the occurrence of the second externally generated
signals.
BRIEF DESCRIPTION OF THE DRAWINGS
The single FIGURE illustrates in diagrammatic form the implantable
and external units forming the system of the present invention.
DETAILED DESCRIPTION OF INVENTION
The FIGURE illustrates, in diagrammatic form, a preferred
embodiment of the present invention including internal and external
units. A dotted line 10, which may represent the skin, separates
the external unit (positioned beneath the dotted line 10) from the
implantable unit (positioned above the dotted line 10). Both the
implantable and external units may be housed, as desired, with the
implantable unit being housed in a manner which will protect its
components from the body environment, in known manner. The dotted
lines 10a and 10b, respectively, represent such housings.
The implantable unit includes a sense amplifier 11, a pulse
generator 12, a demodulator 13, programming logic 14, a reed switch
15 and a stimulation energy delivery system including a lead 16, an
active electrode 17 carried by the lead 16, and an indifferent
electrode 18, together with their interconnections which will be
described more fully below. The external unit includes a pick-up
antenna 20, an amplifier 21, a pulse shaper 22, a display 23, a
flip-flop 24, and AND gate 25, a delay circuit 26, a programming
transmitter 27, a transmitting antenna 28 and a normally open
switch designated generally at 29, together with their
interconnections which will be described more fully below.
Generally speaking, the external unit transmits a programming
signal via transmitting antenna 28, the transmitting signal being
established by programming transmitter 27. The programming signal
is received by lead 16 and demodulated by demodulator 13 to result
in a reprogramming of sense amplifier 11 and pulse generator 12 by
programming logic 14. Pick-up antenna 20 senses stimulation signals
applied to the lead 16, those signals being amplified and shaped to
result in a display at display 23. Display 23 allows an external
monitoring of the stimulation signals applied to lead 16 to
establish that a reprogramming has been accomplished. Additionally,
the signals picked up at pick-up antenna 20 are processed by AND
gate 25 and delay circuit 26, together with a manual input entered
at switch 29 which is operative on flip-flop 24, to establish a
desired relative timing between a stimulation energy signal and a
programming signal.
Sense amplifier 11 and pulse generator 12 are connected to function
as a demand cardiac pacemaker. That is, signals sensed between
electrdoe pair 17/18 resulting from natural heart activity will be
applied to the input of sense amplifier 11 via line 30 to result in
a reset signal being applied to pulse generator 12 to restart its
timing cycle. In the event that natural heart activity is not
detected between electrode pair 17/18 during the timing cycle of
pulse generator 12, pulse generator 12 will deliver a pluse of
stimulation energy to the lead 16 to be applied between the
electrode pair 17/18. The operation of sense amplifier 11 and pulse
generator 12, together with any desired noise rejection circuitry,
output driving circuitry, etc., is known to the prior art. It is
also known to employ a received programming signal, demodulated by
demodulator 13, to result in a reprogramming of pulse generator 12
and sense amplifier 11 via programming logic 14. Such operating
characteristics as pulse rate, pulse width, and pulse amplitude
together with mode of operation, hysteresis, etc., have been
programmed in this manner. It is further known to disable the sense
amplifier 11 during the programming signal, as by closure of the
reed switch 15 in the presence of a magnetic field, to cause the
pulse generator 12 to operate in an asynchronous or fixed rate. The
demodulator 13 may be enabled only during closure of the reed
switch 15 so as to limit the potential for a false programming via
extraneous noise. Each of these features are illustrated by the
interconnections shown with reference to the implantable unit in
the Figure. However, the prior art receiving antenna, which formed
a part of the implantable unit and was typically encapsulated or
housed therewith, is not illustrated in the Figure. Instead, the
lead 16, which may be any of a variety of prior art leads, is
connected directly to demodulator 13 to serve as the receiving
element for the radio frequency programming signals. Thus, the
programming capability is maintained while eliminating a component
previously necessary to accomplish that end. In addition, in the
event that the stimulation signal generating components and the
reprogramming components are enclosed in a hermetically sealed
housing, the use of lead 16 as the receiving element, being
external to the metallic housing, eliminates the prior art
difficulties of metal absorption, reflection and attenuation of
radio frequency energy resulting from the prior art placement of
the receiving antenna within the metallic housing.
The external unit includes a magnet 31 which, when placed in
sufficiently close proximity to the implanted reed switch 15,
results in a closing of the reed switch 15 and an enabling of
demodulator 13 and disabling of sense amplifier 11, as discussed
above. In this condition, the stimulation signal generating
components of the implanted unit will operate in a fixed rate or an
asynchronous mode while the demodulator will accept a programming
signal received at lead 16.
A stimulation signal applied to lead 16 will result in a radio
frequency signal which may be detected by pick-up antenna 20. The
resulting signal may be amplified at amplifier 21 and shaped by
pulse shaper 22 which may include a Schmitt trigger, in known
manner, to be displayed at display 23. Display 23 may be any
conventional display allowing the monitoring of such stimulation
signal parameters as pulse rate, pulse width and pulse amplitude,
for example. Thus, elements 20-23 and 31 of the external unit allow
an external, non-invasive monitoring of the present programmed
state of the pulse generator 12. Of course, if the programmed state
includes operation in the demand mode, magnet 31 may be removed
allowing reed switch 15 to open to determine how often stimulation
signals are delivered as well as the parameters of those
signals.
The output from pulse shaper 22 is applied as one input to an AND
gate 25. The Q terminal of flip-flop 24 is connected to the other
input of AND gate 25 while the output of AND gate 25 is connected
to a delay circuit 26. The output of delay circuit 26 is connected
to the reset terminal of flip-flop 24 and to a programming
transmitter 27. Normally open switch 29 is connected between
flip-flop 24 and a source of positive potential B+ such that
closure of the switch 29 will clock the Q terminal of flip-flop 24
high. Thereafter, an output from pulse shaper 22 resulting from the
detection of a stimulation signal by pick-up antenna 20 will result
in two high inputs to AND gate 25 and activation of delay circuit
26. Delay circuit 26 may be of any type known to the prior art
which will provide an output signal a predetermined time after it
receives an input signal. Delay circuit 26 is activated by the
first stimulation signal appearing on lead 16 that is detected by
pick-up antenna 20 following the closing of switch 29. That is,
closing of switch 29 causes the Q output of flip-flop 24 to go high
resulting in one high input to AND gate 25. Detection of a
stimulation signal on lead 16 results in a high output from pulse
shaper 22 and a second high input to AND gate 25, the resulting
high output from AND gate 25 activating delay circuit 26.
Preferably, the delay of delay circuit 26 is sufficient to delay
its output until the stimulation signal that resulted in its
activation is terminated. Most preferably, the delay is sufficient
to delay the output of delay circuit 26 for a predetermined period
of time following a detected stimulation signal on lead 16. The
predetermined period of time may be established such that the delay
output is rendered during the refractory period of the tissue being
stimulated by the electrode pair 17/18.
As noted above, the output of delay circuit 26 is connected to the
reset terminal of flip-flop 24 to result in a resetting of
flip-flop 24 after the delay of delay circuit 26. In addition, the
output of delay circuit 26 is connected to a programming
transmitter 27 to cause programming transmitter 27 to activate,
after the delay period, to result in the transmission of radio
frequency programming signal via transmitting antenna 28, in known
manner. Programming transmitter 27 is of the type that may be set
to establish one or more of the oprating characteristics of sense
amplifier 11 and pulse generator 12 in cooperation with demodulator
13 and programming logic 14, and may employ any of the radio
frequency techniques known to the prior art.
Obviously, many modifications and variations of the present
invention are possible in light of the above teachings. For
example, the teachings of the present invention are easily
adaptable to a bipolar lead system. One possible adaptation would
be to have the sense amplifier 11 connected to a bipolar mode and
keep the demodulator connected in a unipolar mode with one of the
bipolar leads and indifferent electrode 18. Additionally, pick-up
antenna 20 and transmitting antenna 28 need not be separate
elements. Further, the detection of a stimulation signal need not
be accomplished as described with reference to the Figure.
Alternatively, the stimulation signal may be detected by a skin
electrode which may then be processed in accordance with the
teachings herein to result in a delay of the transmission of the
programming signal. Of course, display 23, while described with
reference to monitoring the programmed state of sense amplifier 11
and pulse generator 12, will also allow a determination that a
desired programming has been accomplished by displaying the desired
parameters following transmission of a programming signal. It is
therefore to be understood that, within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described.
* * * * *